Some decisions invite undesirable behaviour, even if unintentional. Others can encourage desirable behaviour, but they have to be thought through. Think about taking the escalator, or taking the stairs.
These actions are challenging because they have an immediate cost, but generate long-term benefits, and because human decision-making can be skewed to a present bias. Behavioural economics studies these challenges, and was the subject of a State of the Art Lecture given by Philip Oreopoulos of the University of Toronto at the 50th meeting of the Canadian Economics Association. Here is a summary of his talk.